There are a wide variety of light sources in existence, e.g., incandescent lights, fluorescent lamps, solid state light emitters, laser diodes, thin film electroluminescent devices, light emitting polymers (LEPs), halogen lamps, high intensity discharge lamps, electron-stimulated luminescence lamps, etc. The various types of light sources have been provided in a variety of shapes, sizes and arrangements, e.g., A lamps, B-10 lamps, BR lamps, C-7 lamps, C-15 lamps, ER lamps, F lamps, G lamps, K lamps, MB lamps, MR lamps, PAR lamps, PS lamps, R lamps, S lamps, S-11 lamps, T lamps, Linestra 2-base lamps, AR lamps, ED lamps, E lamps, BT lamps, Linear fluorescent lamps, U-shape fluorescent lamps, circline fluorescent lamps, single twin tube compact fluorescent lamps, double twin tube compact fluorescent lamps, triple twin tube compact fluorescent lamps, A-line compact fluorescent lamps, screw twist compact fluorescent lamps, globe screw base compact fluorescent lamps, reflector screw base compact fluorescent lamps, etc. The various types of light sources have been supplied with energy with an Edison connector, a battery connection, a GU24 connector, direct wiring to a branch circuit, etc. The various types of light sources have been designed so as to serve any of a variety of functions (e.g., as a flood light, as a spotlight, as a downlight, etc.), and have been used in residential, commercial or other applications.
With many light sources, there is a desire to effectively dissipate heat generated in generating light.
For example, with many incandescent light sources, about ninety percent of the electricity consumed is released as heat rather than light. There are many situations where effective heat dissipation is needed or desired for such incandescent light sources.
Solid state light emitters (e.g., light emitting diodes) are receiving much attention due to their energy efficiency. A challenge with solid state light emitters is that the performance of many solid state light emitters may be reduced when they are subjected to elevated temperatures. For example, many light emitting diode light sources have average operating lifetimes of decades (as opposed to just months or 1-2 years for many incandescent bulbs), but some light emitting diodes' lifetimes can be significantly shortened if they are operated at elevated temperatures. A common manufacturer recommendation is that the junction temperature of a light emitting diode should not exceed 85 degrees C. if a long lifetime is desired.
In addition, the intensity of light emitted from some solid state light emitters varies based on ambient temperature. For example, light emitting diodes that emit red light often have a very strong temperature dependence (e.g., AlInGaP light emitting diodes can reduce in optical output by ˜20% when heated up by ˜40 degrees C., that is, approximately −0.5% per degree C.; and blue InGaN+YAG:Ce light emitting diodes can reduce by about −0.15%/degree C.). In many lighting devices that include solid state light emitters as light sources (e.g., general illumination devices that emit white light in which the light sources consist of light emitting diodes), a plurality of solid state light emitters are provided that emit light of different colors which, when mixed, are perceived as the desired color for the output light (e.g., white or near-white). The desire to maintain a relatively stable color of light output is therefore an important reason to try to reduce temperature variation of solid state light emitters.
There are a variety of lighting devices that generate heat at a wide variety of different rates. It would be desirable to provide lighting devices in which the amount of heat that can be dissipated can be selected to match the rate of heat generation by each individual lighting device. For example, it would be advantageous to be able to provide a series of lighting devices (or any of the members of such a series) in which each member of the series has a different number of light emitting diodes, resulting in respective different rates of heat generation, and to be able to easily provide the respective lighting devices with correspondingly different rates of heat dissipation sufficient for dissipating the respective different rates of heat generation. It would be desirable to be able to provide incrementally different rates of heat dissipation in such devices.